Small, human-powered watercraft (e.g. kayaks, canoes, dinghies, rowboats, launches, tenders, etc.) are as popular as ever throughout the world for their simple, quiet and economical operation. In recent history, some attempts have been made to motorize such small watercraft, albeit with mixed success, whether due to lack of sufficient power, noisy operation, complex systems or expenditure of significant resources. However, a need persists for a small traditionally human-powered watercraft to have auxiliary and redundant power available.
For example, we have found that there are some hobbyists who have built their own crude electric watercraft. The majority of these projects are undertaken by anglers who enjoy fishing from a small boat, and need mobility without paddling. Most of the time, these anglers use a marine lead acid battery along with a trolling motor to achieve their goals. However, these embodiments are not well suited for portability, as the propulsion system does not have a readily removable and/or retractable feature. Further, the properties of the motor, hull and propulsion system are rather primitive, leading to a very low efficiency (rendering either slow speed, short duration or significant weight from heavy motor and its power source). In this regard, a lightweight traditional craft capable of efficient and quiet motorized operation, having high maneuverability, with a retractable and/or removable motor would be highly advantageous.
Similarly, sea kayaking is another hobby enjoyed by many people around the world. In many cases, hobbyists endeavor a multi-hour or even multi-day kayaking trip and find that their muscles fatigue. In such cases, it would be of tremendous benefit to have a propulsion system on the kayak to assist the kayaker to travel farther and/or faster than that by human propulsion alone. Moreover, some kayakers may lack the endurance for extended kayaking trips, so a self-propelled kayak that gives paddlers a chance to rest would be appealing. A variety of demographic groups, such as anglers, touring kayakers, and wildlife spectators, would also be interested in a self-propelled kayak or other small watercraft.
Using electric power has several advantages. First, it allows the watercraft to enter regulated bodies of water, where gas motors may not be used. Second, it is also quiet, which is important to both anglers and wildlife spectators. Lastly, it is environmentally friendly, which is a characteristic likely very important to most kayakers and those that regularly enjoy the outdoors. Finally, it is significantly less expensive to use electric power instead of petroleum based fuel.
Waterside resorts or rental businesses would also benefit from the development and availability of an efficient, quite, portable electrically powered watercraft for recreational boating. These buyers will have unique needs because a large percentage of their clientele will have minimal boating experience, and as such the traditional paddle may not provide a suitable form of propulsion. By way of example, an electric kayak would be safer than a traditional kayak, since a fatigued kayaker could return to shore using electric power. Likewise, elderly or physically-challenged individuals would be able to participate, whereas traditional human-powered kayaking or canoeing might be too demanding given the physical challenges.
Several attempts have been made to design and build such a motorized watercraft, as exhibited by other patents and publications. For example U.S. Patent Application Publication No. 2002/0195039 (“Anderson”) discloses a motorized kayak having a gasoline powered inboard-style propulsion unit. However, Anderson exhibits several shortcomings in the art, namely: noise and pollution emitted from the combustion engine, the need to carry a fuel in the hull, weight from such a combustion engine and a fuel tank being permanently affixed into the hull of the watercraft, and a severe a lack of steerability, among other shortcomings.
Likewise, U.S. Pat. No. 5,937,785 (“Murray”) discloses a similar inboard-style propulsion unit with an electric motor rather than a combustion engine. However, Murray also exhibits similar shortcomings with respect to its permanent motor and power source weight, its lack of steerability as the thrust from its propulsion system, and like Anderson, the thrust from the propulsion unit cannot be directed to ease steering.
U.S. Patent Application Publication No. 2007/0012236 (“Caples”) discloses a retractable propulsion unit utilizing an electric motor—but such motor is not steerable. In this regard Caples, like Anderson and Murray, exhibits a distinct deficiency in steerability. More particularly, our research and testing has shown that it is very difficult to turn a motorized kayak wherein the propulsion unit cannot be steered. In essence, a human being exerting a force with a paddle or even a rudder (approximately 1/10th of a horsepower or less) is working against the force of a motorized propulsion unit (½ horsepower or greater, likely five, ten or more times the horsepower of the paddle or rudder). Quite simply, a human exerting force on a paddle is an insufficient force to overcome the forward thrust and forward inertia of a motorized watercraft.
Thus, what is badly needed in the art is an electrically powered watercraft having a properly designed retractable propulsion unit. It is preferable that such a retractable propulsion unit be steerable—thereby having the ability for its thrust to be controllably directed in different directions thus compensating for the difference in power between the human and the propulsion unit. In order to stow the propulsion unit, it is frequently necessary to create a cavity in the hull that is exposed to the water. Significant improvements in efficiency can be rendered if the hull can remain streamlined without unnecessary turbulence created by this cavity. Further, significant improvements in portability can also be rendered to the user if such a propulsion unit (and its power supply) are readily removable from the watercraft.
Thus, while a need exists for certain improvements in propulsion, steering, efficiency and portability in small traditionally human-powered watercraft, such needs have not been filled by those practicing in the art.